Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

BDS3 Orthodontics > Aetiology of Malocclusion I N > Flashcards

Aetiology of Malocclusion I N Flashcards

1
Q

what are the 3 general aetiological factors in the formation of a malocclusion?

A
  1. Skeletal issues
    - Size of the jaws
    - Shape and relative positions of the jaws
  2. Muscular issues
    - Form and function of the muscles surrounding the teeth
  3. Dentoalveolar issues
    - the size of the teeth in relation to the size of the jaws
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what does malocclusion result from in the facial skeleton?

A

disharmony in the components of the facial skeleton

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what are the components of the facial skeleton we consider involved in the formation of a malocclusion?

A
  • the maxilla
  • the mandible
  • the alveolar processes
  • the cranial base angle
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what does the transverse view of the face look at?

A

the alignment of the jaws and how they meet

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what genetic factors play a role in skeletal variation?

A

familial studies, particularly those with twins, show there is a genetic component the shape of the jaws and how they relate

particularly in class 3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what environmental factors can play a role in skeletal variation?

A
  • masticatory muscles
  • mouth breathing
  • head posture (up and forward posture = longer facial pattern) (back and downward posture = deep overbite and reduced face height)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

if a patient has weak masticatory muscles, how are they likely to appear?

A

weaker muscles tend to have longer faces and are prone to an anterior open bite

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

if a patient has strong masticatory muscles, how are they likely to appear?

A

reduced lower anterior face height and deep bite

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

how can a patient have abnormal jaws but still be a class 1?

A

they both could be over or undersized, but still relate normally to one another

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what is the class 1 skeletal relationship?

A

the mandible and maxilla relate normally to one another, with the mandible 2-3mm posterior to the maxilla

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what is lateral cephalometry?

A

this is a standardised lateral radiograph of the face and the skull
o it is standardised so that it is reproducible if the patient is positioned in a cephalostat a set distance from the cone and film

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what is the SNA measurement?

A

the angle created by the sella, nasion and A point

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what is the SNB measurement?

A

the angle created by the sella, nasion and B point

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what is the ANB measurement?

A

the angle created by the A, B and N points

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what are the average cephalometric values for a class 1 diagnosis?

A

SNA = 81+/-3

SNB = 78+/-3

ANB = 3+/-2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what are the potential causes of a class 2 skeletal pattern?

A
  1. The mandible being too small (most common)
  2. The maxilla being too large
  3. The mandible being normal sized but places too far back due to an obtuse cranial base angle
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

how will the teeth erupt if a patient has a class 2 skeletal relationship?

A

in a post normal class 2 buccal segment relationship

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

what are the average cephalometric values for a class 2 diagnosis?

A

SNA = usually average but may be increased if the maxilla is prognathic

SNB = <78+/-3 (usually decreased)

ANB = >4 (sometimes >5)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

when is the Eastman correction used and what is it?

A
  • Correct the ANB for a half degree for every degree SNA is over or under the average
  • For every degree OVER 81 -0.5o, and for every degree UNDER 81 +0.5o to ANB

used for when the SNA is larger or smaller than usual

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

what are the potential causes of a class 3 skeletal pattern?

A
  1. Maxilla being too small (most commonly)
  2. the mandible is too large
  3. a combination of both
  4. normally sized jaws but the mandible is positioned too far forwards due to an acute cranial base angle
21
Q

how do the teeth erupt in a class 3 skeletal relationship?

A

in pre normal class 3 buccal segment relationship

22
Q

what are the average cephalometric values for a class 3 diagnosis?

A

SNA = sometimes decreased if the maxilla is retrognathic/hypoplastic

SNB = often average as usually the maxilla is too small but may be increased if the mandible is prognathic

ANB = <1 or negative

23
Q

what is dents alveolar compensation?

A

o the dento-alveolar structures may disguise an underlying skeletal discrepancy
o forces from the lips,cheeks and tongue tend to incline the teeth toward a position of soft tissue balance

e.g. in a class 3, the incisors erupt more vertically to meet anteriorly but this leads to an increased maxillary height

24
Q

what might happen in dent alveolar compensation if there is a reduced cranial base angle?

A

the posterior teeth may erupt more vertically so that there is an anterior open bite

25
Q

how do you assess the vertical jaw relationship?

A

by looking at the FMPA (angle between the Frankfort plane and the mandibular plane)

26
Q

what does the average clinical value of the vertical jaw relationship measure?

A

the upper anterior face height (from glabella to the base of nose) and the lower anterior face height (from the base of the nose to the tip of the inferior aspect of the chin)

27
Q

if done visually, what is the average ratio of the lower anterior face height to the total anterior face height?

A

50%

28
Q

what is the average cephalometric value of the FAMP in the vertical skeletal relationship?

A

27 degrees +/-4

29
Q

what is the average LAFT?TAFH ratio in cephalometric analysis?

A

55%

30
Q

what points are used to measure the UAFH and LAFH in cephalometry?

A

UAFH = nasion to the anterior nasal spine

LAFH = anterior nasal spine to the mention

31
Q

in a long facial type, what will the FAMP and LAFH/TAFH values be?

A

LAFH/TAFH = >55% (i.e. LAFY is greater)

FAMP = >31 degrees

32
Q

in a short facial type, what will the FAMP and LAFH/TAFH values be?

A

LAFH/TAFH = <55%

FAMP = <23 degrees

33
Q

how will a patients face appear in a long anterior face?

A
  1. A steeply inclined mandibular plane
  2. Backward mandibular growth rotation
  3. A tendency for an anterior open bite
34
Q

how will the patients face appear in a short facial type?

A
  1. Shallower mandibular plane
  2. Results in a more defined chin point
  3. The jaws are almost parallel
  4. There is a forward mandibular growth rotation
    - May increase depth of bite over time
  5. Tendency to have a deep overbite
35
Q

what are arch width discrepancies?

A

discrepancies in the correct relative width of the jaws in relation to one another

e.g. the maxilla should always be wider than the mandible

36
Q

what can exaggerate arch width discrepancies?

A

AP skeletal discrepancies

37
Q

what can result from arch width discrepancies?

A

mandibular displacement, bilateral or unilateral buccal segment corssbites and transverse dentoalveolar compensation

38
Q

how would you assess a patients mandibular displacement?

A

look at their teeth in the initial tooth contact, and then get them to slide into intercuspation and observe if there is deviation of the mandible

39
Q

what is mandibular displacement commonly associated with?

A

TMJ disorders

40
Q

if a patient cannot reach a centric occlusion in ICP or RCP, what might they have?

A

a skeletal asymmetry

41
Q

why is a mandibular displacement common in class 3 occlusions?

A

the maxilla bites onto a wider part of the mandible as it is set further back resulting in a lack of intercuspation

42
Q

what is transverse dento alveolar compensation?

A

this is compensation in the transverse plane where the tongue and cheeks force the teeth to erupt on a different inclination to prevent a crossbite

43
Q

how might there be transverse dento alveolar compensation if there is a narrow maxilla?

A

the maxillary molars erupt more flared

44
Q

how might there be transverse dents alveolar compensation if there is a wide maxilla?

A

the lower molars erupt more upright

45
Q

what are the 2 causes of facial asymmetries?

A
  1. dental causes
    - displacement of the normal mandible due to a unilateral crossbite
  2. true mandibular asymmetry
    - hemi-mandibular hyperplasia/elongation
    - condylar hyperplasia
    the whole face may be affected by mild expressions of hemi-facial microsomia
46
Q

how can an arch size discrepancy cause crowding?

A

small jaws and normal size teeth

47
Q

what are the 2 methods of crowding?

A
  • small jaws and normally sized teeth OR

- normal sized jaws and large teeth (macrodontia)

48
Q

what are the 2 methods of spacing?

A
  • large jaws and normally sized teeth

- normal sized jaws and small teeth (microdontia

BDS3 Orthodontics (11 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions